The effect of grid frequency decay transients on pressurized water reactors

This paper describes the effects of loss of reactor coolant flow as caused by power system frequency decay on a Westinghouse pressurized water reactor. A protection scheme employing measurement of coolant flow, and reactor coolant pump power supply voltage and frequency is described. Analyses are presented which provide a basis for a low frequency reactor trip setpoint which adequately protects the nuclear plant, and which does not unduly compromise plant availability.